1. Field of the Invention
The present invention relates to an electronic device package, and in particular relates to a light emitting diode package.
2. Description of Related Art
Light emitting diodes are one kind of semiconductor device, which have a P-type and an N-type semiconductor layer. When a forward voltage is applied to the light emitting diode, electrons flow from electrodes and holes come from electrodes toward an interface between the P-type and the N-type semiconductor layers to combine and produce energy. Then, the energy is released in a light form. Light emitting diodes have several advantages over other conventional light sources such as high brightness, small sizes, lighter weights, lower power consumption and longer operating lifespan, such that they are widely applied to various light sources and display devices.
FIG. 1 shows a cross section of a conventional light emitting diode package. A plastic material 10 formed by injection molding is used to sandwich a metal lead frame 12 to form a carrier for a light emitting diode 14. The light emitting diode 14 is disposed on the lead frame 12 and a conductive wire 16 is used to electrically connect the light emitting diode 14 and the lead frame 12. Then, a depression of the plastic material 10 of the carrier is filled with an encapsulant 18 to cover the light emitting diode 14, to form the conventional light emitting diode package.
However, in the conventional light emitting diode package, the difference between a thermal expansion coefficient of the plastic material 10 of the carrier and a thermal expansion coefficient of the metal lead frame 12 is large. In general, the thermal expansion coefficient of the plastic material 10 is usually about 100 ppm/° C., but the thermal expansion coefficient of the lead frame 12 is usually about 20 ppm/° C. Accordingly, adhesion between the plastic material 10 of the carrier and the lead frame 12 is poor. Thus as the conventional light emitting diode package is exposed to heat and cold, a gap is produced between the plastic material 10 of the carrier and the lead frame 12, such that water vapor may easily permeate through the gap and decrease reliability of the light emitting diode.
Additionally, for the conventional light emitting diode package, a shape of the lead frame 12 is formed from bending by a mechanical process. Accordingly, a gap is easily produced between the plastic material 10 of the carrier and the lead frame 12 to further decrease reliability of the light emitting diode.
Therefore, a light emitting diode package and a fabrication method which can overcome the above mentioned problems of the conventional light emitting diode packages is therefore desired.